The present invention relates to propeller fans in general, and more particularly to improvements in axial flow fans with adjustable blades.
It is known to provide an axial flow fan with means for changing the angular positions of blades to thereby change the volume of displaced gaseous fluids. As a rule, the shafts or shanks of blades in an axial flow fan are mounted in friction and/or antifriction bearings which are installed in discrete housings. The housings are mounted on a hub which is driven to orbit the blades about its axis. The axes of the blades extend radially or substantially radially of the hub axis. The adjusting means for changing the angular positions of blades comprises devices which can rotate the shanks of blades in the respective housings. A drawback of presently known axial flow fans with adjustable blades is that the adjusting mechanism for the blades is very complex, that the compensation for machining tolerances takes up much time, that the hub for the blades is bulky and comprises a large number of complicated parts, and that the energy requirements for rapid acceleration of the fan to normal operating speed are extremely high.